1. Technical Field
The present disclosure disclosed a light emitting device which is especially related to the sidewall of the substrate of the light emitting device.
2. Description of the Related Art
The light radiation theory of light emitting diode (LED) is to generate light from the energy released by the electron moving between an n-type semiconductor and a p-type semiconductor. Because the light radiation theory of LED is different from the incandescent light which heats the filament, the LED is called a “cold” light source. Moreover, the LED is more sustainable, longevous, light and handy, and less power-consumption, therefore it is considered as a new light source for the illumination markets. The LED applies to various applications like the traffic signal, backlight module, street light, and medical instruments, and is gradually replacing the traditional lighting sources.
FIG. 1 illustrates the structure of a conventional light emitting device 100 which includes a transparent substrate 10, a semiconductor stack layer 12 formed above the transparent substrate 10, and an electrode 14 formed above the semiconductor stack layer 12, wherein the semiconductor stack layer 12 comprises, from the top, a first conductive-type semiconductor layer 120, an active layer 122, and a second conductive-type semiconductor layer 124.
In addition, the light emitting device 100 can be further connected to other components in order to form a light emitting apparatus. FIG. 2 illustrates a conventional light emitting apparatus including a sub-mount 20 carrying an electrical circuit 202, a solder 22 formed above the sub-mount 20; wherein the light emitting device 100 is bonded to the sub-mount 20 and is electrically connected with the electrical circuit 202 on the sub-mount 20 by the solder 22, and an electric connection structure 24 that electrically connects the electrode 14 of the light emitting device 100 to the electrical circuit 202 on the sub-mount 20. The sub-mount 20 may be a lead frame or a large size mounting substrate in order to facilitate circuit design and enhance heat dissipation.
Nevertheless, because the surface of the transparent substrate 10 of the conventional light emitting device 100 as shown in FIG. 1 is substantially flat and the refractive index of the transparent substrate 10 is different from the refractive index of the external environment, the total internal reflection (TIR) occurs when a light A emitted from the active layer 122. Therefore the light extraction efficiency from the light emitting device 100 is reduced drastically.